The present invention relates to an air bag system that restrains a vehicle occupant upon a collision of a motor vehicle, for example, so as to protect the vehicle occupant from an impact applied to the vehicle body, and in particular to such an air bag system that is able to restrain the vehicle occupant with high efficiency, and a method of controlling the air bag system.
An air bag system for a motor vehicle as disclosed in U.S. Pat. No. 5,308,113 has been known which includes an inflatable bag, and an inflation-controlling member that is coupled to the bag and serves to control inflation of the bag.
More specifically, a releasable connection of the inflation-controlling member remains intact during initial stages of the inflation process of the bag, so that the inflation-controlling member extends to its initial length, thereby to restrict inflation of the bag. The releasable connection releases during intermediate stages of the inflation process of the bag, so that the inflation-controlling member extends to its intermediate length, and the bag assumes an intermediate shape. A stretchable section of the inflation-controlling member then stretches during the final stages of the inflation process, so that the inflation-controlling member extends to its final length, and the bag assumes a final shape.
With this arrangement, the air bag is able to protect a vehicle occupant who is seated at a location other than a nominal seated position, and also permits the bag and the vehicle occupant to softly or flexibly contact with each other when he/she is seated at the nominal position.
In the known air bag system, however, the vehicle occupant who is seated at the nominal position is restricted and protected by the bag that has inflated to its full size in the final stages, and therefore the maximum amount of gas is always supplied to the bag upon its inflation. Where the vehicle occupant is wearing a seat belt, therefore, the bag that has inflated to its full size may undesirably apply an excessively large restraining force to the chest of the vehicle occupant.